The 14c activity of some ancient peruvian corn was found to be 10 disintegrations per minute per gram of carbon. if present-day plant life shows 15 dpm/g, how old is the peruvian corn? the half-life of 14c is 5730 yr

3400 years. The first thing to do is determine how many half lives the sample has undergone. Assuming that the level of atmospheric carbon 14 has remained consistent over time, the sample has only 2/3rd of the level of activity, so only has 2/3rds of the carbon-14 level. So calculate the logarithm to base 2 of 2/3. log(2/3)/log(2) = -0.17609/0.30103 = -0.58496 This indicates that 0.58496 half lives have expired which is a reasonable number since if 1 half-life had been spent, the level of activity would be half of modern activity. So just multiply the number of half-lives by the half-life. So -0.58496 * 5730 = -3351.835129 Rounding to 2 significant figures gives an estimated age of 3400 years.